Crank and pitman mechanism



3 1,639,334 Aug. 16, 1927. v H FORD CRANK AND PITMAN MECHANISM Filed May25.. 1921 2 sheets-sheet 1 I 1,639,334 Aug. 16,1927. HFORD CRANK AIDPITMAN MECHANISM Filed May 25. 4921 2. Shoots-Sheet 2 Patented Aug. 16,1927.

v UNITED STATES HENRY FORD, OF DEARBORN, MICHIGAN.

CRANK AND PITMAN MECHANISM.

Application filed May 25,

My invention relates to mechanisms embodying a plurality of pitmenco-operating with and radiating from a common crank, and moreparticularly relates to a composite pitman head for a single actingmechanism of this character.

In any single Iacting crank and pitman mechanism, the bearing pressuresimposed on the crank pin by the pitman rod side and cap side of thepitman head, respectively, are unequal; and under ordinary workingconditions where the pitman rod is stressed principally in compression,the principal bearing pressure is lmposed on the pitman rod segment ofthe pitman head. or crank pin hearing. A single acting engine having aplurality of cylinders arranged angularly about the axis of a crankshaft and each provided with a reciprocating piston adapted tocommunicate an impulse directed toward the crank shaft through anindividual pitman to a common crank, and operating under ordinary speedsand pressures; provides an example of a crank and pitman mechanismimposing a principal bearing pressure on the pitman rod segment of thecrank pin bearing and typifies a mechanism to which my present inventionis particularly and advantageously applicable.

The general objects of my invention are to organize and construct asimple and efficient crank and pitman mechanism embodying a plurality ofpitmen co-operating with a common crank, and in which the unit bearingpressureon the crank pin bearing is uniformly distributed and with. aminimum difference between the maximum and minimum pressures present; inwhich the coordination and distribution of bearing surfaces with respectto the force vectors in volfved is brought closer to 'a faultlesscondition; in which adequate bearing wear compensation is provided;inwhich liability,

to cramping and pinching of the bearing is largely reduced if noteliminated; and in which the structure is of simple construction andnon-cumbersome, readily handled and manipulated, and generally free fromtrouble in service and in installation.

Further objects of the invention are: to I provide a composite pitmanhead for plural pitman common crank mechanisms wherein the bearingsurfaces are advantageously coordinated and disposed; to provide acomposite pitman head for a crank and pitman mechanism embodying aplurality of pitmen 1921. Serial No. 472,589.

radiating from a common crank, wherein a maximum bearing surface area-isavailable to those segments of the crank pin bearing to which theprincipal pressures are applied; and to provide a'concentric' pluralpitman head having a composite common crank pin bearing that is freefrom liability to cramping and pinching, that is adjustable for wear,that may readily be lubricated, and the structure of which is simple,compact, durable and economical of production. To these and other ends,my invention may consist in the mechanism of a single acting engine asshown in the drawings, wherein: i

Figure 1 is a fragmentary sectional elevation of the displacement andturning efi'ort mechanism of a single acting engine embodying myinvention;

Fig. 2 is a transverse sectional elevation taken in the plane of theline IIII of Fig. 1 and looking in the direction of the arrows, showingin elevation the common composite pitman head and adjacent ends of apair of pitmen and showing in section the crank pin common thereto andembraced thereby;

Fig. 3 is an elevation corresponding to Fig. 1 of the structure shown inFig. 2, the caps, however, being broken away and their bolts removed;and

Fig. 4 is an elevation corresponding t Fig. 2 of one of the caps alone.

The present embodiment of my invention is shown in the drawings asapplied to a crank and pitman mechanism constituting a simplecombination of a plurality of pitmen with a common crank; and two setsof these n hanism are combined, as shown in Figure 1, 'n the mechanicalsystem of a four cylinder (1 uble crank engine, this illustrating a forof What is generally known as an engine the double-opposed type, and ispresented to illustrate the characteristics of the present invention,which pertains more particularly to the displacement and turning effortsystems present in internal combustion engines of the four-cycle type,Where a plurality of pitmen areiconnected to a single crank of thecrank-shaft; I

The cylinders 1, 2, 3-and 4 are arranged in'a common plane and in mutualparallelism about the 180 degree cranks 5 and .6 of a crank shaftjournaled at 7 and 8, thus setting up the characteristics of adoubleopposecl motor structure, the type employed for illustrating thecharacteristics of the reciprocable trunk piston that is individuallyconnected to its respective crank through a pitman 11 and each of thesepit- 'men is pivotally attached to its piston about the axis of awrist'pin 11 and ]ournaled at its head end about the axis of a crank'pin13 extending between the arms 14 and 15 of the cranks5or 6. r

It will be observed that the cylinders. are arranged in groups abouteach crank circle with outwardly divergent coplaner axes and that theitmen of each group of cylinders radiate rom a common crank pin withwhich they mutually coo erate but about each body may be faced andlined' with a bearing metal bushing 22 and the convex back of theannularly se mental axially extending end 23 of these bodies may beutilized to carry the arcuate cap bearing surfaces 24 that are formedco-axial with and in opposed relation to the crank pin bearing whichthey are individual y journaled. Ac-

cording to my invention a composite pit-g man head is provided for eachgroup of pit-jglpin,

surfaces.

The caps 21 should be equal in number to the pitmen employed and,especially when the arcuate length of the bearing surfaces arerelatively short, one cap section should be rigid with each of thepitman bodies and should substantially circumpose the crank pin axis.Thus, although for three or more pitmen itv may be desirable to form asurface 24 on each sideof the pitman rod and to provide a plurality ofsplit annular cap sections angularly surrounding these surfaces anddivided axiallythereof, an individual' cap section of each pitman beingangularly rigid therewith; yet, when but two a single surface 24 on eachalternate men and their crank pin; and since in the" side onlyof each ofthe two pitman rods may present embodiment of my invention the' be used,and a pair .of segmental caps 21 groups above referred to constitutepairs,

I such as the alined cylinders 1 and 2, and

their itmen; a' double composite pitman head or the pitmen of a pair ofcylinders co-operating with a common crank and having an included anglebetween their axes and about the crank circle of approximately 180degrees, is illustrated and described in detail. In this pitman head afull length crank in bearing for each pitman is formed withn the pitmanhead body of each pitman whereas the cap bearin s for the pitmen areformed externally of t eiibodies and conprovided, each being adapted toco-operate Z withone surface 24 alone and to be secured directly to acorrespondingly formed port1on of its pitman body. The cap may, in

centric with their crank in bearings. Furthermore, for avoidingiability-tocramping, each pitman has elements of its crank pinconstra-imnent surfaces disposed on opposite sides of .a plane passingthrough the 1 crank in axis normal to the pitman length.

To t is end I attach, rigidly, to the crank pin end of each pitman rod11 a body 20' that is'generally arcuate'in form, that is, a

segment of an annulus of suitable radial thickness, having an axiallength co-extensive with the length of the crank pinand having anangular "length approximating a the arcuate length of its crank pinbearmg surface, hereinafter more fully set forth.

The capping means, whereby the head formation produced by'the assemblyof the pitis held assembled and the man segments, Est b bodies seated onthe crank pin,

uted on both sides of 'a plane normal to the pitman length and passingthrough the crank pin axis; and includesa plurality of circumposed casections, such as 21, one or more rigid wit and one or more movable withrespect to each pitman body.

The concave crank pin bearing surface of this instance, be considered tobe in part pitmen co-operate with a single crank .virtually integralwith the pitman body, and

thus it is clear that the constrainment afforded by the capping meansmay in either case be symmetrical with respect to the pit man rod andproportional to the sum of the axial lengths of a pair of surfaces 24,one on either side of the pitman plane.

In other words, that portion of each pitman formation that is active inproducing the head assembly has a total arcuate length of bearingsurface greater than the similar length of the bearing surface of thebody 20 on the crank-pin, with the total arcuate' length produced byseparated bearing surfaces located respectively on opposite sidesof aplane normal to the pitman length and extending through the crank pinaxis, such plane, -in the form of the invention illustrated, extendingthrough the clearance spaces 31'presently referred to.

Accordingly, in the structure illustrating n1 invention in its presentembodiment, each 4 o the pitman bodies 20 on its end opposite to that onwhich its surface 24 is formed, is provided at each of its angularextremities with one of a pair of transversely extend- .ing ears 25formed integral with the body;

and each of the caps 21, as shown in Fig. 4, is similarly provided witha pair of corresponding ears ,2(i matching with andseating on the earsof the body. A screwthreaded bolt 27 provided with a nut 28 passesthrough each of the matching pairs of ears 25 and 26 and holds thecapsecurely cap and body ears to facilitate the setting I and adjustmentof the caps with respect to their bodies and thus also bearing surfacescircumposed about the crank pin axis.

A clearance space 31 extending angularly about the periphery ofthe-crank pin is provided between the adjacent angular ends of the crankpin bearing segments of the succes'sive pitman bodies. Thisaocomodatesthe differential pivotal movement of the adjacent bodies about the crankp1n axis and therefofe its angular extent is dictated by I the. maximumrelative deflection of adjacent pitmen and preferably increased by asuitable addendum. 2

A similar clearance is rovided for portions of adjacent relative ymovable parts that are liable to interfere. Thus when the bolts 27 areplaced relatively close to the crank pin surface, their shanks mayinterfere with the relatively movable body and accordingly the grooves32 are provided,

these grooves being disposed and formed to receive and clear theadjacent bolt shanks when the deflection between the correspondingpitman is a maximum.

The angular value S of the clearance 31 and all similar clearances maybe represented by the formula:

Where: S denotes the angular value of the clearance in radian measure;

' movable surfaces, (such as 33-34) when at my invention to co-operatewith a common; 'crank pin, the arcuate length B of each the surface maybe made co-extensive with- L is the pitman length in terms of the crankcircle radius; a

X is the angle in radians, included'jbetween the respectively adjacentcylinder axes;

C denotes an addendum added to insurethe separation of the opposedrelatively their limitiof approach. A practical minimum value for thisquantity maybe .005 of the crank pin diameter.-

Where the pitmen of two co-axlal slides or pistons are adapted w-accord1ng to crank pinbearing segment, that is the angular length ofthe surface between'its extremi-' ties 33-33 or 34-'34, is preferablyextended through its maximumlefiective angle, e. g.,

the projected area of the'crank pin. In this case the angular extent ofthe crank pin surface not embraced by the bearing segments will, ifequally divided, be more than adequate to provide the clearance s ace31.

since each interval will be eater t an the necessary value of S. 11general, the length B of the various pitman se .ents' is the result of aportioningthe di erence between 2 pi ra ians and the sum of the spaces Sto the various pitmen; and thus the arcuate length B of the body segment20 of each of a plurality of pitmen 11, having their respective axes ofreci rocation uniformly spaced aboutthe crank circle may be representedgenerallyby the formula:

where: B is in radian measure-and N is the number of pltmen.

The angular length of' the bearing surface l to,

29 of the cap 21 1. e., the angular distance between its terminalsurfaces'3535 is preferably, substantially co-extensive with' the extentand disposition of the surfaces '24 that are to be embraced thereby.

Havin thus fully described my invention,

what I c aim is zy 1. In a crank and pitman mechanism, the

combination with a crank pin and a plurality of radiating pitmen, of acomposite pltman head common to the crank in and the pltmen, said headembodyin a p l urality of angularly spaced crank pin caring seg- I mentsseating on the crank in and each individually attached to one o theitmen, and capping means co-operating with ing segments for completingthe pitman the bearhead formation and its constrainment, said.-

formation including peripheral and cire-umposed elements presentingcorrespondingly, co-operating'bearing surfaces for each pitmandistributed on both sides of a plane normal to the pitman length andpassing through. the crank pin a'xis, a segment of a circumposingelement bein carried by one pitman and superposed w th respect toa} 3segment of another pitman with the bear ing surfaces of the elementsegment-and the bearing se ment extending on arcs, differing in theength ofthe arc radius.

.2. In a crank and pitman mechanism", the i combination with a crank pinand a plurality of radiating pitman rods, of an arcuatecrank pln bearingsegment rigid with each;-

of the rods'and extending transversely both-dlrections therefrom andhaving a concave crank in bearing surface the .axial' length of WhlCh isco-extensive with that of,

the crank pin, a plurality of convex cap;

of the bearin surfaces ,formed exte'riorl extendm ends of thesegments anI co-axial with their crank and .slidingly engage their pin bearingsurfaces, .a pluralityof caps adapted to circ ing surfaces, one of saidcaps being rigidly attached to each of said segments' 3. In a crank andpitman mechanism, the combination with a crank pin and a pair ofradiating pitman rods, of a composite pitnian head common to the crankpin and the pitman rods, said head comprising a pair of segmentalbodiesadapted to be alternately disposed in spaced relation about thecrank pin and each individual to and rigid with one of said rods, eachof said bodies extending transversely of its rod in both directions andaxially of the crank pin, a concave se mental crank pin bearing formedin each of said bodies, a convex cap bearing surface formed exterior-1yon a mutually alternate extending end of each of the bodies concentricvwith their crank pin bearing surface, and a pair of caps each adapted toengage with 'one' of said cap bearing surfaces and to be secured to theadjacent portion of the opposed body.

In testimony whereof I aflix my signature.

HENRY FORD.

